EPR spin-probe studies of thermal phase transitions in liposomes are usually carried out at X-band (9.5 GHz). X-band studies suffer from low spectral resolution; for non-deuterated nitroxides, only the high-field component is split. Better resolution, as well as measurement of rotational correlation times, can be obtained only with specially designed nitroxides. In this project, we demonstrate and discuss the prospects of high-frequency (95 GHz) EPR for obtaining rotational and partitioning information about spin probes in lipid systems. We monitored the thermal phase transition for aqueous dispersions of the phospholipid DPPC (1,2-2,2,6,6-tetramethylpiperdine-1-oxyl) partitioned between both membrane (hydrocarbon) and aqueous phases. W-band completely resolves the entire TEMPO EPR spectrum in both aqueous and hydrocarbon environments. Therefore the TEMPO partition coefficients can be determined with better accuracy at W-band. The more informative high-frequency EPR data were analyzed using a fast rotational model to derive the rotational correlation times during the thermal phase changes in the DPPC membrane.